Physics - Senior Secondary 2 - Heat Energy Measurement

Heat Energy Measurement

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TERM: 1ST TERM

WEEK: 2

Class: Senior Secondary School 2
Age: 16 years
Duration: 40 minutes for each of 5 periods
Date:
Subject: Physics
Topic: Heat Energy Measurement
Subtopics:

  • Concept of specific heat capacity
  • Measurement of specific heat capacity (solid and liquid)
  • Significance of specific heat capacity

SPECIFIC OBJECTIVES:
By the end of the lesson, students should be able to:

  1. Define specific heat capacity and understand its significance in heat energy.
  2. Describe the method to determine the specific heat capacity of solids and liquids.
  3. Perform experiments to determine the specific heat capacity of solids and liquids using the method of mixture.
  4. Analyze the results from experiments and calculate the specific heat capacity.

 

INSTRUCTIONAL TECHNIQUES:

  • Explanation
  • Demonstration
  • Hands-on experiment: Determining specific heat capacity of solids and liquids
  • Questions and answers

 

INSTRUCTIONAL MATERIALS:

  • Calorimeter
  • Thermometer
  • Weighing balance
  • Water
  • Hot plate
  • Beakers
  • Ice
  • Physics textbook
  • Whiteboard markers

 

INSTRUCTIONAL PROCEDURES

PERIOD 1-5

 

PRESENTATION

STEP 1: INTRODUCTION

  • The teacher introduces the concept of specific heat capacity: the amount of heat required to raise the temperature of a unit mass of a substance by 1°C.
  • The teacher explains that different substances have different specific heat capacities.

 

STEP 2: EXPLANATION

  • The teacher explains the formula for specific heat capacity:
    Q=mcΔTQ
    where:
    • QQ is the heat energy absorbed or released (in Joules),
    • mm is the mass of the substance (in kg),
    • cc is the specific heat capacity (in J/kg°C),
    • ΔT\Delta T is the change in temperature (in °C).

Solved Example:
If 200g of water is heated, and the temperature rises by 10°C, the heat absorbed by the water is calculated as follows:

  • Mass of water, m=0.2 kgm = 0.2 \, kg
  • Change in temperature, ΔT=10°C\Delta T = 10°C
  • Specific heat capacity of water, c=4186 J/kg°Cc = 4186 \, J/kg°C (constant)

The heat absorbed, Q=mcΔTQ becomes:
Q=0.2×4186×10=837.2 JQ = 0.2 \times 4186 \times 10 = 837.2 \, \text{J}
So, the water absorbs 837.2 Joules of energy.

 

STEP 3: DEMONSTRATION

  • The teacher demonstrates how to calculate the specific heat capacity of a solid (metal) using the method of mixture.
  • The teacher heats a metal and places it into a known mass of water in a calorimeter.
  • The change in temperature of the water is measured, and the heat lost by the metal is equal to the heat gained by the water.

Solved Example:

  1. Suppose a 100g piece of metal is heated to 80°C and placed into 200g of water at 20°C.
  2. After reaching thermal equilibrium, the final temperature is 30°C.
  3. Use the formula to calculate the specific heat capacity of the metal.
    • Mass of water = 200g = 0.2kg
    • Specific heat capacity of water = 4186 J/kg°C
    • Temperature change for water = ΔT=30°C−20°C=10°C\Delta T = 30°C - 20°C = 10°C

Heat gained by water:
Qwater=mcΔT=0.2×4186×10=837.2 JQ = 837.2

Heat lost by metal:
Qmetal=Qwater=837.2 JQ

Now, using the formula Q=mcΔTQ
837.2=0.1×cmetal×(80−30)837.2
837.2=0.1×cmetal×(50)837.2
cmetal=837.25=167.44 J/kg°Cc_

Thus, the specific heat capacity of the metal is 167.44 J/kg°C.

STEP 4: HANDS-ON EXPERIMENT

  • The students will conduct an experiment to determine the specific heat capacity of a solid (metal) and a liquid (water).
    Procedure for solid:
  1. Heat a metal sample and place it into a calorimeter with water.
  2. Measure the initial temperature of the water and metal.
  3. After placing the metal in the water, measure the final temperature of the water.
  4. Calculate the specific heat capacity of the metal using the formula.

Procedure for liquid:

  1. Use the same procedure as for solids, but this time heat water and measure its temperature change when mixed with another liquid.

 

STEP 5: NOTE TAKING

  • The teacher writes a summary note on the board for students to copy.

 

NOTE

Specific Heat Capacity:

  • Specific Heat Capacity is the amount of heat energy required to raise the temperature of 1 kg of a substance by 1°C.
  • The formula for heat energy is:
    Q=mcΔTQ
    where cc is the specific heat capacity, mm is the mass of the substance, and ΔT\Delta T is the temperature change.
  • The unit for specific heat capacity is J/kg°C.
  • Significance:
    • High specific heat capacity: Substances take longer to heat up or cool down (e.g., water).
    • Low specific heat capacity: Substances heat up or cool down quickly (e.g., metals).

 

EVALUATION

  1. What is specific heat capacity?
  2. Write the formula for specific heat capacity.
  3. Describe how to calculate the specific heat capacity of a solid.
  4. Perform the calculation for a metal sample heated and placed in water.

CLASSWORK:

  • Complete the calculations for the specific heat capacity of the solid and liquid in your experiment.
  • Compare the specific heat capacity of different materials based on your results.

 

CONCLUSION:

  • Review the students’ experiments and results.

Encourage students to reflect on the practical applications of specific heat capacity in real-life situations, such as cooking or climate control.